The document FR-A-2,506,872 describes a constant velocity joint of this type in which each radial arm of the tripod is capable of sliding between two portions of plane and parallel surfaces of the transmission joint body by means of an articulation element carried by the arm of the tripod and which comprises two opposite and parallel plane faces each of which interacts with one of the plane surface portions of the transmission joint body with the interposition of a row of bearing needles held in a cage.
Such a design of a telescopic transmission joint is particularly advantageous in so far as it makes it possible to filter out the vibrations coming from the drive member and in so far as the joint is practically free of periodic internal friction.
Various methods for implementing the design principle of such a joint have been proposed, such as, for example, those described and represented in the document FR-A-2,583,476.
It is nevertheless noted that the transmission joint body is difficult to produce economically in so far as it is necessary to form, in the transmission joint body, parallel and plane pairs of raceways for the bearing needles as well as faces or grooves for guiding and holding the cages of needles. It is also necessary to produce spherical tripod arms.
The object of the present invention is to propose a transmission joint implementing the design principle mentioned previously, in which the transmission joint body is particularly simple to produce.
Another object of the present invention is to allow standardisation in the manufacture of transmission joint bodies of the constant velocity type so that one and the same joint body comprising bearing races in the form of axial grooves of circular-profiled cross-section may be used with a tripod whose articulation elements comprise cages of bearing needles as has been explained previously, or with a tripod whose articulation elements are spherical rollers mounted to swivel on the arms of the tripod.
To this end, the present invention proposes an articulated transmission joint of the sliding type comprising a transmission joint body and a tripod comprising three radial arms evenly distributed about the axis of rotation of the tripod and each of which is capable of sliding between two parallel and plane surface portions of the joint body by means of an articulation element which is carried by the arm of the tripod and which comprises two parallel and opposite plane faces each of which interacts with one of the plane surface portions with interposition of a row of bearing needles held in a cage, characterised in that the joint body comprises three bearing races each comprising two tracks each of which consists of a component comprising a plane surface portion which interacts with the bearing needles of one of the rows of needles and comprising a plane surface portion which interacts with the bearing needles of one of the rows of needles and comprising a convex cylindrical surface portion whose axis is parallel to the plane surface portion and which interacts with a complementary concave cylindrical bearing surface formed in the joint body with respect to which it is capable of pivoting, and in that each arm of the tripod comprises a journal on which the intermediate articulation element is mounted to revolve about an axis parallel to its opposite plane surfaces.
According to other characteristics of the invention:
each intermediate articulation element is axially immobilized with respect to the associated journal; PA1 each track is axially immobilised with respect to the joint body; PA1 each intermediate articulation element is a cylinder section whose end faces are perpendicular to the axis of the cylinder and which is pierced through its middle with a hole whose axis is concurrent with and perpendicular to the axis of the cylinder and which receives the journal; PA1 each of the cages of needles comprises at least one longitudinal guidance and holding flank which extends in a direction perpendicular to the axes of rotation of the needles and which interacts with at least one complementary guidance surface of the associated track; or PA1 each cage comprises two parallel guidance and holding flanks between which there are received two parallel and opposite flanks of the associated track.